1. Field of the Invention
The present invention relates to a ringed tubular protective sheath, more specifically comprising two open shells, referred to as the outer and inner shells, which have the same diameter and one of which, the outer shell, has an opening smaller than the diameter so as to engage by elastic deformation over the inner shell in a closed position.
2. Description of the Related Art
It should be recalled that the bundle of electric cables provided in a car is conventionally formed by electric wires with a round cross-section which are assembled in wire strands. Once these strands have been formed, the bundle is provided with various protective elements before being fixed onto different elements of the vehicle, such as the engine and the car body.
Ringed tubular sheaths are one of the types of protection for bundles of electric wires commonly used in the car industry. The ringed tubular sheaths, formed by moulding an extruded tube into a succession of rings, are conventionally produced from extruded plastics materials, such as polypropylene, polyamide or polyesters. These sheaths provide effective resistance to abrasion and crushing, while maintaining a high level of flexibility which facilitates the production and packaging of the protected cabling, and the installation thereof in the vehicle. However, it is difficult to thread the strand in the ringed sheath, in particular over long portions of said sheath. This is why split ringed sheaths are often used, i.e. ones which are cut along a straight longitudinal line at the end of the production process. This enables electric wires and cables to be subsequently introduced directly through the split into any region of the sheath.
The split ringed sheaths may comprise more or less complex closing systems so as to prevent wires from escaping from the tube in regions where the split tends to reopen. These closing systems have been found to be relatively ineffective in regions with low radii of curvature, or cause the sheath to become too rigid. An example of this type of sheath is provided by document EP-A-860 921.
The split ringed sheaths can also be taped up completely once they have been positioned over the bundle of cables, and this locks the split effectively, but requires an additional operation from the person installing the cables.
Another solution, which is known for example from EP-A-268869, involves using an assembly consisting of a first open shell which is positioned around the bundle of electric cables and a second open shell with the same diameter as that of the first shell, excluding the thickness of the wall. The second shell, also referred to as the outer shell, has an opening which is smaller than the diameter so as to engage by elastic deformation over the first shell, also referred to as the inner shell. During engagement, the outer shell opening undergoes tensile deformation until it passes the point corresponding to the diameter of the inner shell. After this point, the outer shell opening returns to its unstretched position. In document JP 2000-115942, the two shells are connected by a longitudinal strip to remedy the drawback of an assembly consisting of two separate elements which complicates the logistics, the cut along the protective element and the installation operations for the person laying the cables.
The solution disclosed by these two documents allows the ringed tubular sheath to be held in the closed position by the opening of the outer shell merely returning to the unstretched position. In other words, no other locking means is required to hold the two shells in the closed position. However, this solution requires a relatively high level of force to engage the outer shell on the inner shell, since the inner shell does not facilitate the insertion process and in contrast tends to oppose the deformation of the outer shell opening until it has passed the point corresponding to the diameter.